Audio Engineering
P.A. Systems Amps are designed to produce it's maximum power (W) to a given amount of impedance (Ohms). This impedance is most often 4 Ohms, and is usually marked close to the speaker outputs. This value indicate that the amp will produce it's most power (W) when the speakers connected to it apply totally 4 Ohms. Due to the formula P = (U^2) \ R, every value above this will give less power (W) to the speakers, and if the connected value is less than this the amp might overheat since it gives more power (W) than it is designed for. To connect more speakers to the same amplifier will commonly increase the connected impedance, and decrease the power (W) out, and therefore not increase the sound level. Modern amps have a "sikring" which turn the amp off, or automatically decrease the volume if it pulls to much current from the "nettspenning", or if the temperature gets to high. Impedance of two speakers is calculated by the formula for two shunt-resistances. Rt=(R1*R2)\(R1+R2) Impedance of more speakers is calculated by the general formula for shunt-resistances (1\Rt) = (1\R1) + (1\R2) +...+ (1\Rn) A mixer will often have two different impedance values, one for the microphone amps, and another value for the speakers out. Mixers without microphone amps will usually have two input-impedances, "Low impedance" and "High impedance". XLR-connectors are low-impedance, and jack-connectors are high-impedance. If connecting the wrong signal to the wrong input will not brake anything, but just lower the input volume and cut away some of the incoming frequencies. There are two types of equalizers, graphic and parametric. Graphic EQ's has a set of predefined frequencies where the volume can be adjusted. Parametric EQ's have variable frequency-controllers, and will affect a chosen area around the selected frequency as well. "Delefilter" is used in all speaker-systems with more than one element, and divides the incoming signal into two or more separated signals containing different frequencies. This will stop the low frequencies from reaching the high-pitch element. If a "delefilter" is inside a speaker, it is usually passive, but if it is connected to a voltage source by itself, it is active. That means that they contain own amplifiers for each separate signal. A "delefilter" will usually therefore increase the sound quality. Dictionary: Acoustic Suspension A closed speaker cabinet which use the air behind the element in the cabinet as a spring to control the resonance Attenuation Reduction Auxiliary Send the electrical signals in a detour Baffle A straight surface to put speakers on Balanced plug An electrical plug supporting grounding, such as the stereo jack- or XLR plugs. This is to reduce unwanted noise. Bandwidth The area of frequencies that is covered by a speaker or a filter Basket The metal frame of a speaker Bi-amping ??? Bridging Is to combine both left and right side of an amp to one more powerful mono-channel Clam "Feilspilling" Clipping 1) Can occur from an amp when the input gain is to high, or the output volume is set to high and then the amp is sending to powerful current so that it becomes DC which is sent to the speakers. 2)When the volume to the speakers is to high, and the element can't move as much as the signal tells it to. This results in noise, and leads to "sprenging". Continous Average Power ?? Crossover Network (filter) "Delefilter" Også kalt Electronic and passive crossover Damping May refer to headphones Cue May refer to headphones Distortion Measured in prosent Impedance Resistance in AC-circuits, measured in ohms. Receiver impedance should be 7 times higher than sender impedance Insert A connection where the electrical signal is cut from it's original path, and sent somewhere else TONO Is a Norwegian organization which collect composer fees from performed live-music NBC Is a Nordic organization which collect composer fees from musical recordings of any sorts "2-Way" A speaker with two elements Microphones: Dynamic Microphone Consist of a movable membrane attached to a movable coil. The coil is placed in a magnetic field produced by a permanent magnet, and so voltage occur when the membrane is vibrating due to sound waves Condenser Microphone A movable membrane serve as one conductor, and a permanent block serve as the other conductor in a capacitor. The signal produced like this is very weak, and need additional voltage to run a small integrated amplifier Ribbon Microphone Is made out of a strong permanent magnet with a small aluminium ribbon is placed between the poles. When this ribbon is vibrating as due to sound waves, a small current will be induced in the ribbon. Microphone Sensitivity Is a measurement for how much voltage is induced when a sound pressure of 1 Pa is applied to the membrane. Impedance Most microphones are low-impedance, resulting in a small AC-resistance somewhere in between 150-600 ohms. Low-impedance microphones produce less background noise, and is therefore preferred. An amplifier must have at least five times higher impedance than the microphone it is connected to. This is to prevent decibel loss, and a better noise\signal ratio. A synthesizer or guitar-pick ups are high-impedance, and such devices use commonly a jack-plug to prevent plugging it into wrong impedance. Low-impedance devices uses normally a XLR-plug. Proximity Effect The fact that close-up microphones produce more low frequencies, easily heard at distances of less than 50cm. Pop-Sounds p, t and b can make a "utblåsning" of the microphone. S-Sounds Some people have sharp s-sounds, and it can be avoided by talking slightly to the side of the microphones as those sound waves are "retningsvirkende" DI box Consist of a transformer which transforms a high-impedance source into a low-impedance and balanced signal. An active DI-box has a built-in amplifier, as the output-voltage becomes very weak. "Polar patterns"? : Omni directional - Pick up sounds from all directions. Commonly rarely used in music-recording. Uni Directional 1) Shotgun - Picks up sound only from straight in front of the microphone. 2) Cardioid - Picks up sound in a "heart-shaped" pattern, with most from the front of the microphone. Drums: A drum is a cylinder-shaped "shell", made out of wood, "kompositt"?, plastic, steel or steel"legeringer". Tree"sorter": Maple (Lønn) Hard wood. Good resonance nice "finish"? Warm and rich sound with an even frequency-spectrum. Birch (Bjørk) Kompact wood. Gives 10% less bass-tone, and 20% more high pitch sounds, compared to maple. Mahogany (Mahogni. From USA or Honduras) gives 20% more bass-tone then maple. Warm sound because of this. Beech (Bøk) Somewhere between maple and birch. Oak (Eik) Bright, "gjennomtrengende" tone with high attack. Less common wood types: Basswood (Lind), Poplar (Poppel), Philippine Mahogany (Filipinsk mahogny) or combinations of wood types. Shells (Trommeskjell) The smoother shells are on the inside, the more resonance the drum gives. Using thick shells means that it is mostly the skin which gives the tone. Thin shells gives more resonance, and has a lower pitch than thick ones. Drums with reinforcement rings (forsterkingsringer) has a shorter decay (etterklang) and more powerful attack in the middle-pitch area. Skin Clear (Transparent) Bright sound with "overtoner". Nice attack which cut through the soundscape. Coated (White) More powerful attack, warmer sound and lower high-pitch than the Clear. This type is nessicary for using "visper" "2-Layers" (2-lags) Reduce "overtoner", deep and heavy sound which can handle harder playing, but less "feel". Underskin is usually clear for tom-toms, example Remo Ambassador, Genera G1. For snare is it custom-made for "seider" Hoops\Rims (Ringer) Flanged\Triple flanged hoops (valsede) gives a deep and fat sound, mostly used for tom-toms. trickier to tune than Die Cast Hoops. Steel rims give a deeper pitch than aluminium. Die Cast Hoops (Støpte) Thicker and stronger than Flanged rims. Gives more smooth tuning, and better response and less "overtoner". A bit drier sound and more powerful attack than Flanged rims. Wood Hoops (treringer) Can sound as both above dependent on it's thickness. The higher pitches are more reduced than the above.